The present invention relates to a method of heat treating cast articles and to cast articles which have been so treated. More particularly, the present invention relates to a heat treatment process for increasing the impact resistance of metal and metal alloy castings by removing hydrogen from the casting, and to the improved metal and metal alloy casting so produced.
Cast materials having desirable attributes, e.g., corrosion resistance, are often not available for some practical applications because the applications require impact resistances beyond conventionally available ranges. Further, the process of casting a material commonly reduces the impact resistance of the material utilized to form the casting. Accordingly, there is a need for a heat treatment process whereby the impact resistance of selected cast articles can be increased beyond the bounds set by conventional casting and heat treatment processes.
Some conventional heat treatment processes include a hot isostatic pressing step followed by a post-weld stress relief step. Unfortunately the post-weld stress relief step frequently reduces the impact resistance of the cast article. Accordingly, there is a further need for a heat treatment process which eliminates or reduces the loss in impact resistance commonly resulting when a post-weld stress relief step follows a hot isostatic pressing step.